Browsing by Author "Akdogan, Hulya"
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- Effect of operating conditions on physical characteristics of extruded rice starchPublication . Tomás, Rui; Oliveira, Jorge C.; Akdogan, Hulya; Mccarthy, KathrynThe effect of screw speed, flow rate, barrel temperature and added moisture on physical characteristics of high moisture extruded rice starch was studied. the product physical characterization was made by measuring density, final moisture content and the maximum load force in a puncture test. Rice flour containing approximately 1.5% protein and 6% moisture was mixed with 55–65% (w/w) water and extruded in a co-rotating twin screw extruder with a slit die. A two level factorial design was used to analyse each parameter. It was found that added moisture was the most important variable affecting the force-deformation curve maxima, with the interaction between added moisture and barrel temperature exhibiting a less significant effect. Added moisture and flow rate each affected density, with the interaction between added moisture and screw speed showing a less significant effect. Temperature and flow rate affected final moisture interactively with added moisture, which was evidently the most important variable.
- Rheological properties of rice starch at high moisture contents during twin-screw extrusionPublication . Akdogan, Hulya; Tomás, Rui L.; Oliveira, Jorge C.A semi-empirical model to predict the apparent viscosity function of high moisture rice starch melt was developed. The model coupled the influence of extruder operating parameters on characteristics of the fluid and on conditions of rheological measurements. The model for apparent viscosity considered power law dependency of shear rate, and exponential dependency of temperature, moisture content, and screw speed. A MPC/V-30 co-rotating twin-screw extruder and a slit die/torque rheometer combination were used. Operating parameters varied between 175 and 275 rpm for the screw speed, 80 to 100 °C for extruder and slit die temperatures, 570 to 650 g/kg solution for moisture content, and 2 to 7 kg/h for the mass flow rate. The fit between the experimental results and model was good. Die temperature was the most important parameter influencing the viscosity of rice starch during extrusion.